An organic light emitting device is a device which includes a thin film which contains a fluorescent or phosphorescent organic compound and is interposed between electrodes, in which an exciton of the fluorescent or phosphorescent compound is generated when a hole and an electron are injected from the respective electrodes and which makes use of light radiated upon return of the exciton to its ground state. The recent progress of an organic light emitting device is significant, and the device suggests its potential to use in a wide variety of applications because of the following reasons. The device shows a high luminance at a low applied voltage. In addition, the device has a variety of emission wavelengths. Furthermore, the device can be a thin, light-weight light emitting device with high-speed responsiveness.
However, at present, an optical output with additionally higher luminance, or additionally higher conversion efficiency has been needed. In addition, the organic light emitting device still has many problems in terms of durability. For example, the device changes over time owing to long-term use, and deteriorates owing to an atmospheric gas containing oxygen, or to humidity or the like. Further, assuming that the device is applied to a full-color display or the like, the device must emit blue light, green light, and red light each having good color purity, but the problems concerning the color purity have not been sufficiently solved yet.
In the meantime, compounds related to the compound of the present invention are disclosed in J. Chem. Soc. 3920 (1964), Compt. Rend. 258 (12), 3387 (1964), Tetrahedron 30, 813 (1974), and Monatsh. fur Chem. 129, 1035 (1998). However, in each of J. Chem. Soc. 3920 (1964) and Compt. Rend. 258 (12), 3387 (1964), research has been conducted mainly on the carcinogenicity of a compound having an azabenzofluoranthene skeleton. In addition, Tetrahedron 30, 813 (1974) describes the emission spectrum of an unsubstituted azabenzofluoranthene compound having a nitrogen atom at a specific position. However, the spectrum has a light emission peak in an ultraviolet region, so the compound may be lowly useful as a light emitting substance.
In addition, organic light emitting devices utilizing a compound having a diazabenzofluoranthene skeleton obtained by introducing two or more nitrogen atoms into a benzofluoranthene skeleton are disclosed in Japanese Patent Application Laid-Open No. 2001-160489, Japanese Patent Application Laid-Open No. 2003-212875, and Japanese Patent Application Laid-Open No. 2006-16363. However, Japanese Patent Application Laid-Open No. 2001-160489 and Japanese Patent Application Laid-Open No. 2003-212875 each describe a compound having a fused diazabenzofluoranthene skeleton, so a light emitting material the luminescent color of which is limited to a luminescent color having a wavelength longer than that of a blue color, in particular, to a red color is provided. In addition, Japanese Patent Application Laid-Open No. 2006-16363 describes that the compound described in the document is used mainly as an electron transporting material, and partly describes that the compound is used as a blue light emitting material. However, the luminous efficiency of the device disclosed in the document is remarkably low.
In addition, Japanese Patent Application Laid-Open No. 2000-311786 describes an organic light emitting device using a compound having an azanaphthoanthracene skeleton obtained by: causing a benzene ring to fuse with a benzofluoranthene skeleton; and introducing one nitrogen atom into the resultant. However, the application of the compound is limited to a green light emitting material owing to the skeleton of the compound.
The present invention has been made with a view to solving such problems of the prior art as described above, and an object of the present invention is to provide a material for an organic light emitting device showing a light emission hue with an extremely good purity and outputting light having high luminance and a long lifetime with high efficiency.
Another object of the present invention is to provide an organic light emitting device that can be easily produced at a relatively low cost.